DL_BLKOFFSET
if (DL_BLKOFFSET(&lab, blkno) == 0 && size % secsize == 0) {
secoff = DL_BLKOFFSET(&lab, blkno);
offset = DL_BLKOFFSET(lp, partoff + DOS_LABELSECTOR);
offset = DL_BLKOFFSET(lp, partoff + DOS_LABELSECTOR);
offset = DL_BLKOFFSET(lp, partoff + DOS_LABELSECTOR);
offset = DL_BLKOFFSET(lp, partoff + DOS_LABELSECTOR);
offset = DL_BLKOFFSET(lp, partoff + DOS_LABELSECTOR);
offset = DL_BLKOFFSET(lp, partoff + DOS_LABELSECTOR);
offset = DL_BLKOFFSET(lp, partoff + DOS_LABELSECTOR);
offset = DL_BLKOFFSET(lp, partoff + DOS_LABELSECTOR);
offset = DL_BLKOFFSET(lp, partoff + DOS_LABELSECTOR);
offset = DL_BLKOFFSET(lp, partoff + DOS_LABELSECTOR);
offset = DL_BLKOFFSET(lp, partoff + DOS_LABELSECTOR);
rlp = (struct disklabel *)(bp->b_data + DL_BLKOFFSET(lp, partoff));